Photochemical internalization of transgenes controlled by the heat-shock protein 70 promoter

Photochem Photobiol. 2006 May-Jun;82(3):809-16. doi: 10.1562/2005-11-07-RA-731.


Photochemical internalization (PCI) is a targeting technique that facilitates endosomal escape of macromolecules, such as transgenes, in response to photochemical treatment with endosome/lysosome-localized photosensitizers, such as disulfonated meso-tetraphenylporphine (TPPS(2a)). In gene therapy this leads to enhanced transgene expression. Moreover, photochemical treatment generally activates transcription of stress-response genes, such as heat-shock proteins (HSPs), via stimulation of corresponding promoters. Therefore, we used HSP70 (HSPp; a promoter from the HSP family gene) and investigated whether the PCI stimulus could also activate HSPp and thereby stimulate transcription (expression) of the HSPp-controlled transgene internalized via PCI. Using human colorectal carcinoma and hepatoma cell lines in vitro, we showed that TPPS(2a)-based photochemical treatment enhances expression of cellular HSP70, which correlated with a photochemically enhanced expression (approximately 2-fold, at PCI-optimal doses) of the HSPp-controlled transgene integrated in the genome. Furthermore, PCI enhanced expression of the HSPp-controlled episomal transgene delivered as a plasmid. However, in plasmid-based transfection, PCI-mediated enhancement with HSPp did not exceed the enhancement achieved with the constitutive active CMV promoter. In conclusion, we demonstrated that the PCI-relevant treatment initiates HSP70 response and that the HSP70 promoter can be used in combination with PCI, leading to PCI-enhanced expression of the HSPp-controlled transgene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Endocytosis
  • Genetic Therapy / methods
  • HSP70 Heat-Shock Proteins / genetics*
  • Humans
  • Photochemistry*
  • Plasmids / administration & dosage
  • Plasmids / pharmacokinetics
  • Porphyrins / pharmacology
  • Promoter Regions, Genetic*
  • Transfection / methods*
  • Transgenes
  • Up-Regulation / drug effects
  • Up-Regulation / genetics


  • HSP70 Heat-Shock Proteins
  • Porphyrins
  • di(4-sulfonatophenyl)diphenylporphine